An apparatus for stacking folded printing products is known from Swiss Patent Specification 623,287 or the corresponding U.S. Pat. No. 4,229,134. These references disclose a conveyor device, by means of which printing products are conveyed up against limiting fences of a prestacking space. The prestacking space is limited at the bottom by two slide plates, on which the printing products are deposited on top of one another to make prestacks, each formed from a number of printing products. Underneath the prestacking space there is a rest table which is equipped with a lifting and lowering device and which is pivotable respectively through 180.degree. about a vertical axis.
A first prestack formed in the prestacking space is deposited onto the rest table, lifted to a little below the slide plates, by moving the slide plates apart from one another. The rest table is subsequently lowered by the amount of approximately the height of the prestack, and to form a further prestack the slide plates are pushed against one another again. The rest table is pivoted through 180.degree. about the vertical axis and subsequently lifted towards the slide plates, so that the printing products of the first prestack are pressed, in order to form an essentially horizontal rest for the next prestack. The rest table is now lowered again, until a small gap forms between the first prestack and the slide plates arranged above it. As soon as the second prestack is ready in the prestacking space, the slide plates are opened again and the second prestack is deposited onto the first prestack rotated through 180.degree..
The rest table is now lowered once more, the slide plates are closed, and the two prestacks lying above one another are pressed against the slide plates as a result of the lifting of the rest table. This operation is repeated until a pressed finished stack composed of a specific number of prestacks arranged above one another lies on the rest table. With this known apparatus, although printing products can be laid on top of one another to form finished stacks having the necessary stability to be transported away, this nevertheless requires a specific processing time.
An apparatus for the stacking of printing products fed with their fold forward is know from U.S. Pat. No. 3,507,492, and in this rests are arranged on a revolving pulling member and are moved from the top downwards past the exit end of the conveyor device. Each rest is composed of parallel L-shaped brackets, one leg of each of which forms a stop for the folds of the printing products. The particular bracket located in the middle has, on its other leg inclined slightly relative to the horizontal, a rest element which is raised in relation to the legs of the other brackets. The first printing products deposited on the rest in succession are thus bent slightly in a roof-shaped manner.
During the lowering of the rest, the bottommost printing product comes to rest, with its edge region located opposite the fold, approximately centrally on a supporting element of fixed location, the roof-shaped bend becoming more pronounced in order to prevent the printing products from collapsing. The associated lifting of the edge regions opposite the folds guarantees that the folds bear firmly against the stop. During the further movement of the rest, each printing product is still supported only at its ends on the fold and at the edge located opposite this. The pronounced bending of the printing products prevents them from collapsing as a result of the pressure forces which are considerable with this type of support. When the printing products run off from the supporting element, each printing product is released individually at its edge located opposite the fold, so that, with the pronounced bend being cancelled, it can swing down again onto the brackets or onto the printing products already lying on them. During the further lowering of the rest, the finished stack passes onto a roller conveyor, by means of which it is conveyed away. With this known apparatus, stacks aligned on the same side as the folds can certainly be formed. But the stack height is restricted, since no further measures at all are taken to give the stack greater stability for transporting away. Thus, with this apparatus it is impossible to eliminate the larger thickness of the printing products in the region of the folds by the pressing of part stacks and/or by stacking these on one another so that they are rotated 180.degree. relative to one another. The bend of the printing products is also cancelled again for transporting them away.